Modern printers use a variety of inks to generate images from data. These inks may include liquid ink, dry ink, also know as toner, and solid ink. So-called “solid ink” refers to ink that is loaded into a printer as a solid, which is typically in stick or pellet form. The solid ink is melted within the printer to produce liquid ink that is supplied to a print head for ejection onto media or an intermediate member to generate a printed image from image data. These solid ink printers typically provide more vibrant color images than toner or liquid ink jet printers.
A schematic diagram for a typical solid ink imaging device is illustrated in FIG. 1. The solid ink imaging device, hereafter simply referred to as a printer 100 has an ink loader 110 that receives and stages solid ink sticks. The ink loader 100 has a plurality of feed channels in which the ink sticks are placed. Typically, a feed channel is provided for each color of ink used in the printer. For example, a color printing machine has a feed channel for each of the black, cyan, yellow, and magenta colors that are used for color printing.
The ink sticks progress through a feed channel of the loader 110 until they reach an ink melt unit 120. The ink melt unit 120 heats the portion of an ink stick impinging on the ink melt unit 120 to a temperature at which the ink stick melts. The liquefied ink is supplied to one or more print heads 130 by gravity, pump action, or both. Printer controller 180 uses the image data to be reproduced to control the print heads 130 and eject ink onto a rotating print drum 140 as image pixels for a printed image. Media 170, such as paper or other recording substrates, are fed from a sheet feeder 160 to a position where the image on the drum 140 can be transferred to the media. To facilitate the image transfer process, a pressure roller 150, sometimes called a transfix or transfer member, presses the media 170 against the print drum 140. Offset printing refers to a process, such as the one just described, of generating an ink or toner image on an intermediate member and then transferring the image onto some recording media or another member.
In some offset printing processes, the intermediate member is brought to a stop so the transfix member can be brought into contact with the intermediate member to form a nip. The leading edge of the media is then fed into the nip as the intermediate member is driven to commence rotation of the member. The rotation of the intermediate member also drives the free-wheeling transfix member so the two rotating members push the media through the nip for the transfer of the image from the intermediate member to the media. While stopping the rotation of the intermediate member facilitates the coordination of the media and transfix member with the intermediate member, it reduces the number of images that can be generated by the printer. Consequently, offset printing processes have been developed that continue to rotate the intermediate member while coordinating the movement of the media and transfix member with the intermediate member.
While these offset printing processes increase printing productivity, they also introduce additional mechanical stresses to the transfer process. One issue is related to the movement of a stationary transfix member into engagement with the rotating intermediate member. The inertial load of the stationary transfix member requires a brief period of time for the intermediate member to bring the transfix member up to the appropriate speed for transfer of the image. Additionally, some slippage between the two members may occur as the rotating intermediate member imparts its driving force to the transfix member. The impact of the stationary transfix member on the rotating intermediate member also puts some stress on the motor driving the intermediate member. Responding to the repetitive load of the stationary transfix member being applied to the intermediate member over the long term may reduce the operational life of the motor.